Campus da FEUP Rua Dr. Roberto Frias, Porto Portugal T F © 2009 Integração na rede eléctrica de veículos eléctricos F. J. Soares 2009 Julho 29

© 2009 Introduction Electric power systems are facing a new challenge: the integration of Electric Vehicles (EVs) in the electricity grids Uncertainties related to when and where EVs will charge will become a critical issue for electricity networks operation For home charging, 3 different charging approaches can be adopted: –Dumb charging approach – EVs’ owners are completely free to connect and charge their vehicles whenever they want, being the cost of the electricity constant along the day –Dual tariff policy – is given the possibility to EVs‘ owners charge their vehicles at a lower price, during valley hours –Smart charging strategy – a hierarchical control structure manages EVs charging according to grid’s needs 2Ciência 2009

© 2009 Steady-state case study (MV network) Residential MV grid 3Ciência 2009 EVs energy demandRegular energy demand

© 2009 Steady-state results 4Ciência 2009 –Dumb charging approach - 10% allowable EVs integration –Dual tariff policy – 14% allowable EVs integration (considering that 25% of the EVs only charge during the cheaper period – valley hours) –Smart charging strategy – 52% allowable EVs integration (considering that 50% of EVs‘ owners adhered to the smart charging system) (assuming 1.5 vehicles per household – vehicles within the grid)

© 2009 Steady-state results 5Ciência 2009 Daily lossesLoad diagrams with 52% EVs

© 2009 Steady-state results – branches’ congestion levels overview (peak hour) 6Ciência 2009 No EVsDumb charging – 52% EVs Dual tariff – 52% EVsSmart charging – 52% EVs

© 2009 Conclusions from the steady-state study Low voltages are the limiting factor to further EVs deployment, for all charging strategies. The system can handle the penetration of EVs up to 10%, without changes in the electricity network, if a dumb charging approach is used. The dual tariff policy improves the integration capability of this grid up to 14%. This value can be higher if a dedicated and dynamic dual tariff is created for EVs. The smart charging approach proved to be the most effective one, as by applying a simple set of rules EVs deployment capability was increased to 52%. 7Ciência 2009

© 2009 Dynamic stability case study (small island) 8Ciência vehicle per household 2150 vehicles 323 (15%) EVs Scenario 1Scenario 2 P Total load (kW)2172 P load (kW)1770 P EV load (kW)402 P EV available (kW)851 Pwind (kW) P sync1 (kW) P sync2 (kW) Scenario 1Scenario 2 P Diesel1,2 (kW)1500 P Diesel3,4 (kW)1800 P Wind (kW) P PV (kW)100 Installed power Valley hour operation (load plus generation dispatch)

© 2009 Dynamic stability case study – sudden win shortfall 9Ciência 2009 Sudden shortfall on wind speed may jeopardize current power quality standards under EN for isolated systems It is a limiting factor to the integration of Intermittent Renewable Energy Sources Disturbance applied to the case study

© 2009 Conclusions from the dynamic stability study It is possible to verify that this system improved dramatically its performance when EVs were used for frequency control. Electric vehicles interfaced with the grid in a smart way can increase robustness of operation to power system dynamic behaviour. The presence of a considerable amount of storage capability connected at the distribution level also allows the operation of isolated distribution grids with large amounts of IRES and/or microgeneration units connected to it. 10Ciência 2009

© 2009 Final remarks Smart charging is to charge in the right place at the right time, thus a communication infrastructure will be needed: –Using smart meters is the most rational option –6 millions of smart meters will be deployed in portugal in a near future (InovGrid Project) 11Ciência 2009